Depending on the design of the mold. This continues until the weld lines in plastic injection molding disappear. The thermo-rheological findings were used to investigate the sources of weld line weakness. Flash: All plastic injection molds contain parting lines, which create the potential for small amounts of molten plastic to escape the mold cavity’s boundaries. Remedies: Raise the temperature of the mold or molten plastic. Cold Slug: First material to enter mold during injection. Examples of different causes of PVC pipe failure. Weld-line is a defect that arises in injection molding when two or more flow fronts collide. 8 mm (32 threads per inch) Use a trapezoidal or buttress thread. The thickness of the part plays an important role in how difficult the molding process will be. Meld and knit lines are actually both different types of weld lines. The influence of knit-lines on the tensile properties of injection molded parts. Molding parts with multiple gates will almost certainly produce a weld line at right-angles to the line joining the two gates which could cause the weld lines to be exceptionally weak (see Figure 1. Knit Line Injection Molding is a process that allows manufacturers to produce parts more quickly, accurately, and at less cost than traditional injection. Causes 1. สาเหตุรองของการเกิดปัญหาการเกิดประกายเงิน (silver streak) 1. The recommended minimum production volume for injection molding is 500 units. incomplete filling or shorts. Learn Injection Molding Glossary with Plastopia: Using actual molded parts (with images) as examples. Weld lines, created in the areas of collision of two flow fronts of plastic in the injection mold cavity, are the reason of lower mechanical properties and a worse surface condition of molded parts. "As soon as that part or material is stressed, it can be real conducive to fracture, cracking, breaking, just because of the way it's been molded. The melt is forced to split up during filling of the cavity. Because they can be shut off independently you can control flow fronts and knit-line locations. Weld line defects – also known as knit lines – is a defect that occurs when the injected plastic meets within a mold. Influence of injection-molding parameters on the morphology and mechanical properties of glass fiber-reinforced polypropylene composite. A weld line (weld point, flow line or a knit line) forms when separate melt fronts travelling in opposite directions meet. This article will discuss the importance of injection molding nozzles and what makes a good nozzle for a molding or injection. Whereas conventional injection molding uses. Injection molded plastic begins its journey through the part tooling via an entry section called a. DOI: 10. In fact, for a 32-cavity mold, the flow rate in this example drops down to 0. Product designers encounter a wide range of challenges when. The part is cooled in the mold until it is solid enough to be ejected. SPI surface finishes are the most common set of injection molding finishing standards around the world with over 12 different grades. Knit Lines in Injection Molding. The quality of the weld line can be improved through optimized processing conditions, increased mold and melt temperatures, and increased injection speed toInjection molding, producing, and forming resin materials are three core components of injection molding technology. Mold flow analysis is a software simulation that can show how resin will fill the mold during the injection molding process. Weld lines may appear like seams or scratches, but that is not what they are. In addition, the company is now providing three. In the injection molding process, knit lines are a common occurrence when two or more plastic flow fronts collide and solidify, resulting in a visible seam or line on the molded part. – Change the thickness of the product. matte or smooth texture on the part’s surface gives a more desirable aesthetic and hides small imperfections such as knit lines, flow lines, shadow marks, and sink marks that were caused by the mold. Weld lines are also known as “stitch lines” or “knit lines”. Below is a list of items that should be checked both during normal molding operations and if defects are detected. In this way, the mold supports distribute the force and minimize the stresses on the mold plates. a specific area on one side lens, a warp line, and a weft line. The part weight x number of cavities + runner weight should. 060 and 0. (1. These lines occurs usually around holes or obstructions and cause locally weak areas in the molded part. When injection molding complex parts, often knit-lines are formed during the mold filling stage. Three terms that often get mixed up are weld, meld, and knit lines. Knit lines form when two or more plastic flow fronts collide and solidify or “knit” during the molding process. menu. 0mm) throughout will ensure that the parts cool evenly and will prevent warping. The best we can hope for is to pressurize the knit or meld line better through the combination of melt temperature, mold temperature, flow rates, and holding pressures. The mold settings can run flawlessly until employees consistently open the machine for inspections, interrupt cycle times, or cause. Submarine gates are another injection molding types of gate that is located below the surface of the part, typically on the underside or back of the part. 5. Weld lines have a significant effect on manufactured products. In the process of injection molding, when the wall thickness of the product is large, the cooling speed of the outer surface is faster than that of the central part. (Overpacking. Weld / Knit Lines; Assumptions. The area generally has lower strength than the other areas of the part. Also discussed are weld and meld lines and their effects on molded. Influence of injection-molding parameters on the morphology and mechanical properties of glass fiber-reinforced polypropylene composite. Formation of knit line. Weld or Knit lines are a plane or section in an injection molding part where the flow of molten plastics meets from different. 030- to 0. In addition to the main factory and development. Injection moulding is a manufacturing process that melts, injects and sets plastic into a metal mould. As these flow fronts come together. 17. In the 1947 book, Injection Molding of Plastics, the late Dr. CURE: Run the mold in. Adjust the design for the flow pattern to be a single source flow. Such molds or tools aren’t intended to be used in operation. 1050 Walnut Ridge Drive. The point of meeting creates a weak spot because the edges of the molten plastic, already cooling, don’t mix together very well. In spite of its cosmetic attributes, a bad knit line can significantly. Knit lines, weld lines, mold lines, or flow lines in injection molding are faint lines that become visible on certain plastic parts. Weld and meld lines are generally caused by holes or inserts in the part, multiple gates, variable wall thickness or hesitation and. As a result, molten plastic takes the injection mold core and cavity shape. Plastic injection force exceeding the clamping pressure of the press. Weld Lines-3 Ways for Detecting and Correcting. In the plastic injection moulding industry, we work with materials that are by-products of oil refinement and moulds made of metal casting, so our terminology is bound to be at least slightly confusing. TWIM=Thin Wall Injection Molding; TSL=Toys,Sports and Leisure; NB=No Break; IMR=Inter Material Replacement. In this way critical areas of the interface in regard to the lack of interdiffusion and the inappropriate molecular orientation were found to be placed near. Weld lines, knit lines, and meld lines are terminologies to describe the imperfections of finished parts in plastic injection molding processing. pdf), Text File (. Knit lines. Knit lines occur at points where resin flows converge after molding around an obstruction or protrusion within the mold, usually away from the gate area. In the case of mold. However, product designers relying on this molding method encounter various challenges during tool design and development. I am working on a thin PC/ASA injection moulded component which has a tendency to snap at the Knit-point (the final point of travel at which the…Here are a few of the most common defects that may occur in plastic injection molding — and how product teams can avoid them. However, with any practice, when the proper care and planning aren’t taken, problems can occur, and with injection molding, knit lines are one of the most common problems. The adverse effect of knit-line formation on the mechanical properties of thermoplastics has been well documented for unfilled materials. Solution: Increase the injection pressure or speed. Undercuts add cost to tooling and molding, which is recommended to eliminate or minimize as possible. Operating Conditions • Fast injection fill speeds, supporting short injection times (1–3 s), especially in thin sectionsGate and Knit Line Locations<br />. BURN MARKS Burn Marks: burn marks can occur when the design of a plastic part, and the subsequent injection mold design, causes air to be trapped during the injection (or filling stage) of the molding cycle. Solution: Increase the injection pressure or speed. When assessing issues with injection molded parts, we want to make sure some core aspects of molding are checked. Fewer knit lines are produced and a smaller amount of fiber-length degradation is noticeable when compared to injection molding. Also, since this part will likely be painted or chrome plated, knit lines are a concern. To prevent knit lines, injection molders can increase the temperature of the molten resin to prevent solidification from starting too soon, and increasing injection speeds and pressure are also potential solutions. Knit lines and other aesthetic characteristics of the part are strictly related to the plastic’s temperature during molding, so efficient filling time is essential for achieving proper welding lines and quality parts. The knit line is generally opposite the gate in thermoset. The mold settings can run flawlessly until employees consistently open the machine for inspections, interrupt cycle times, or cause temperature. Troubleshooting Injection Molding Weld Lines. Thanks to the low air counter pressure in the cavity, this allows injection parameters to be managed in a larger window, optimizing injection time, part aesthetics and mechanical characteristics. 5 mm) is ideal, according to injection molding engineer Jack Rulander of Protolabs in Maple Plain, MN. Temperature is another factor that can cause weld or knit lines in injection molding. This defect is caused when the polymer resin is injected into a mold and flows around a solid piece and forms when the resin collides back together without completely fusing back together. Flow lines are off-color lines, streaks, and other patterns that appear on the surface of a part. 120 in. Rynite® PET is usually processed with melt temperatures between 280 to 285 °C (535 to 545 °F) . Knit line / Meld. An edge gate introduces material at the main parting line, or where the two halves of the mold meet, with a perpendicular runner. Expand. To study the weld line formation of colliding flow fronts the filling of a mold cavity was simulated. Comprehensive. First, an injection mold with triangular inserts was built to study the influence of meeting angles on material properties at the weld line. If the part design’s wall thickness is constant, the magnitude of the plastic’s velocity will be the same at every. Plastic injection molding is a complex and highly intricate process. 26 = 0. Here are some reasons why design is important for injection molding. Redesign the mold: Redesigning the mold to. Reduce the barrel temperature and increase the injection pressure. 1 in. Since the intention is to preserve fiber length in LFRTs by reducing. Plastic Injection Molding Part Design Guidelines, Plastic part Design Guidance, Parting Line Draft Undercuts Wall Thickness & Uniformity Bosses Gussets and Ribs Radii and Corners Material Shrinkage Gating Ventings Knit/Weld Lines. Because injection mold design and processing is complex, a set solution will not solve all problems. Flow Lines Knit or Weld Lines Cavity Gates Table 1 Knit line in a multi-injection-point cavity. Weld lines are formed during cavity. Recent developments were oriented on the analysis of the mechanical performance at local (knit lines and welds) and bulk (molded part) areas, with the influence of molding and welding conditions. a knit line will form 180°on the opposite side from the gate location. And the lead-time for overmolded and insert molded parts is 15 days, a bit longer than FacFox’ single-part injection molding turnaround, but still much faster than traditional insert molding. From: Polylactic Acid (Second Edition. The quality of the answer is directly proportional to the information we have to work with. Some are: Knit lines (discontinuities where two flows merged, creating a weak point)Those are knit lines, formed when two opposing flows of material join together in the mold cavity. It is. The specimens with a weld line at the center were obtained by double gate molding and the specimens without a weld line wereTherefore, changing the edges and corners of the mold core to make it buffer transition and keep the melt flow stable can prevent the occurrence of wavy lines. With plastic finishing plugs and end caps, we can help you keep your products protected while giving. The Mold Tools toolbar provides tools for creating mold tooling (cores, cavities, etc. Misra A. Injection Molding: How to Set Second. Weld lines, also known as knit lines or meld lines, occur when two or more flow fronts meet during the plastic injection molding process. Figure 1: Knit lines in a cover plate. N174W21430 Alcan Dr Jackson, WI 53037 262-677-9700; 16685. When injection molding complex parts, often knit-lines are formed during the mold filling stage. Macromol Symp 1988;21/21: 489-500. ”. In places where the plastic flows around a solid piece of the mold, from a simple circle to forming complex shapes like rings or squares. Inadequate injection pressure can result in knit lines and a surface that. mold venting is at the last filling point, whereby, while the melt flows forward in the cavity, air and gases flow out through the valve. Our glossary of terms provides definitions for a wide range of injection molding terms. Also known as a knit line, this is the point at which two flow formations meet and are unable to. Over the years, I have developed two separate “5M” systems. Mold bases, ejector plates, and some cavities (if nickel or chrome plated to prevent rust). injection-molding machine (Arburg allrounder 320C, Germany). To avoid walls that are too fat or too thin, designing a wall thickness between 0. The weld line can either be a minor cosmetic issue. Injection molding is typically a better choice for more complex parts, while compression molding is a great option for relatively simple designs, including ultra-large basic shapes that cannot be produced using extrusion techniques. The resulting line has the. These knit lines affect the parts aesthetics, but also they generally decrease the strength of the part. This is easier to accomplish on. There is high defect rate (surface defects/knit line). Knit Lines 11: 1. , the Weld line or Knit line or Meld line is the line where two flow fronts meet when there is the inability of two or more flow fronts to "knit" together, or "weld", during the molding process. 2) Vents in an injection mold should let the air out, but not the liquid plastic. Knit lines, holes, part configuration and the talent of your molder all come into play. In working with the injection molding service offered by Protolabs, you provide. See full list on fathommfg. They have their origins in material choice, part design, tooling, and processingIn the injection molding process, knit lines are a common occurrence when two or more plastic flow fronts collide and solidify, resulting in a visible seam or line on the molded part. This range can be affected by the part wall thickness, melt temperature, mold temperature, injection speed, hold/pack pressures and also the time between molding and measuring. Knit Lines. A weld line, also known as a knit line, is a visible line or mark that occurs in an injection-molded part where two or more melt fronts meet and fuse together during the molding process. Knit lines are most common downstream of holes created in parts where the molten material meets. Circular Loom Machine; Raschel Knitting Machines; Shade Net Making Machinery; Inspection Machines; Non Woven Production Line. Depending on the design of the mould and the material being injected, a knit line may: present no problem at all, be a cosmetic issue, or cause a potentially. Obstructions in the part create weld lines or knit lines during injection molding. Criens}, journal={Materials Chemistry and Physics}, year={1986}, volume={14}, pages={69-83} }A structural automotive sub frame component ( 10 ) that is formed from a sheet molding compound having carbon fibers. As. A knit line in a plastic injection-molded part is created when two separate plastic flows meet within the mold and "resolidify" along their interface. In the 1947 book, Injection Molding of Plastics, the late Dr. Trapped gas is one of the most common causes of part burns, and can also lead to short shots and voids, blemishes and discernible knit lines that weaken the part. Injection. Weld or knit lines are perhaps the most common and difficult injection molding defect to eliminate. This can enable the manufacturer to increase the molten plastic temperature at the front of each flow and avoid the occurrence of weld lines. The injection molding design process, much like all industrial design processes, deals primarily with the creation, look, and feel of a product. A weld line can also be called a knit line. Knit and Meld lines are inherent to plastic injection. The injection molding was carried out in a DK-Codim 175/410 injection molding machine. Near-Net-Shape Molding enables us to eliminate knit lines, add undercuts, increase options for geometry and tolerances, and reduce tooling cost for low. A knit line is any line, visible or not, where two resin flows meet. ) Mold Analysis Tools. When these areas are visible, it can pose no problem at all to the piece, be nothing more than a cosmetic flaw, or can be. Knit line / Meld line / Transfer line Discoloured line where two flow fronts meet Mould or material temperatures set too low (the material is cold when they meet, so they don't bond). Notched weld lines then remain near the cavity walls. Melt temperature does. To learn more about us or to get a quote, click here or call 1-888-893-1587 now. The injection molding process offers a vast array of plastic resins to work with. “A knit line in a colored part will result in glaring visual-effect problems, while a knit through a glass-filled part would have a negative effect on both the aesthetics and the performance,” agrees Kurt Weiss, manager of part performance and new material introductions at GE Plastics. This will helpTroubleshooting Injection Molding Weld Lines. As these flow fronts come together. In the plastic injection moulding industry, we work with materials that are by-products of oil refinement and moulds made of metal casting, so our terminology is bound to be at least slightly confusing. Learn more. spelling: injection molding) is a process for producing parts by injecting molten material into a mould, or mold. Injection Molding Problems and Solutions (17/17) – Weld or Knit Lines Sep 27, 2022 Injection Molding Problems and Solutions (16/17) – Warpage Sep 15, 2022. Injection moulding can be performed with a host of materials mainly including metals (for which the process is called die-casting ), glasses, elastomers, confections, and most commonly thermoplastic and. It is important when selecting an injection molder that the right process conditions are used to reduce or eliminate the effects of. Plastic melt and mold temperature. They are formed downstream through holes, and between multiple gate locations. [1] Here are a few ways to prevent knit lines in your plastic parts: Increase material temperature: Higher temperatures on both materials prevent one section from cooling too quickly. Reduce the screw speed and adjust the backpressure. Design bosses with an outer diameter equal 2x the nominal diameter of the screw or insert. Short shots and knit lines are two phenomena that are caused by using highly viscousHowever, they can also create weld lines or knit lines in the part where the flow fronts meet. land and using maximum vent depths to get them as close to self-cleaning as possible. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. Yet a smooth finish sometimes actually highlights flaws like knit lines and blemishes in the part. 040 and 0. Meld and knit lines are actually both different types of weld lines. Weld lines can significantly reduce ultimate tensile strength (UTS) and fracture strain of talc filled polypropylene (PP). Depending on the design of the mold and the material being injected, a knit line may: present no problem at all, be a cosmetic issue, or cause a potentially serious structural problem. He is currently a tooling manager for a large, multi-plant molding and manufacturing company. Material contamination, for example, can cause several molding issues. Compression-molding is also suitable for ultra-large basic. To briefly describe, weld lines are also called knit lines. By altering the part design, it may be possible to just have one flow front, and avoid multiple flow fronts having to come together. Holes in plastic parts are normally cut with a router (or drilled if round. 27-ounce shot size to 600-ton with a 105-ounce shot size. Causes: Weld lines are caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic. This can result in cosmetic defect or a weak point in the part. Exploring common molding defects and. 160"). อุณหภูมิของพลาสติกเหลวสูงเกินไปจนก๊าซหรือความชื้นแยกตัวออกมาได้. For instance, three widely used processes are insert molding, overmolding, and undercuts. Once the plastic cools, the mold is removed, and the object is ready for post-processing. POROUS MOLD MATERIALS. Based on the resin temperature, filling speed, and resin, there is a variation in the knit lines. Anisotropy. 5 inches) dispersed throughout the structural automotive sub frame component ( 10 ). The total amount of scrap being produced during injection molding will usually be higher than that for compression molding because of the additional material loss created. The data suggest that either local sample thickening or grooves form at knit line when complete section solidification takes place first at weld zone or. By altering the part design, it may be possible to just have one flow front, and avoid multiple flow fronts having to come together. Let’s review what causes meld and knit line imperfections, how they’re different, and how they affect part durability. Inadequate venting. incomplete filling or shorts. A knit line is any line, visible or not, where two resin flows meet. Table 2 lists the<br /> properties of common tool steels and the typical mold components for which they are<br /> used. Designers are able to specify seamless design features with compression molding. weak knit lines and fracture points. The primary rule is to apply 1 degree of draft per. What Are Knit Lines in Injection Molding, and How Do You Prevent Them? - RJG, Inc. 7. Mold cores can be machined from a solid piece of copper alloy or inserted to aid in construction or allow for easier replacement if a com-ponent would ever be damaged in molding. These defects are not visible, like small. placed usually in the areas last to fill, near knit lines, as well as on the runner system. A good injection mold design will take all of these factors into consideration, ensuring that the final product looks great. 250 in. 3 /sec of material into a mold, don’t think the material is going into each cavity of a multi-cavity mold at the same 14. 1016/0254-0584(86)90019-2 Corpus ID: 136712450; Impact strength of knit-lines in injection moulded parts @article{Criens1986ImpactSO, title={Impact strength of knit-lines in injection moulded parts}, author={R. The Bottom Line You might have come across the aforementioned terminology before and did not know what any of the words meant. Learn how to troubleshoot weld lines in injection molding. Product designers encounter a wide range of challenges when creating and developing molded parts, such as stress factors, warp, and those pesky knit lines. Knit Lines and Resins A knit line is any line, visible or not, where two resin flows meet (see Figure 2). shows some obvious locations for vents, a brief molding trial should be conducted to observe where the gas voids occur. 2020-01-1306. 5 to 3. And often, the mold is the same color as the plastic polymer, or can appear that way due to a lack of contrast caused by difficulties lighting the inside of the mold. (See Fig. Contact us. Having uniform wall thickness makes it possible for the melted plastic to fill the mold evenly, therefore not creating a part with warp, sink, thin knit lines, or other defects. May happen at first shots while mold is being dialed in. PAPER ABSTRACT: Desktop injection molding machines and stereolithographic print ed molds make hands-on injection molding production possible in design studio classrooms and labs. To learn more about us or to get a quote, click here or call 1. More about the knit lines in injection molding. In addition, the force of the gas holds the appearance side of the part in contact with. This month, we covered an array of topics including injection mold venting, business strategies and runnerless micro molds. S. A knit line, also. Learn how small changes to an injection molding design like wall thickness or material choice can lead to more durable parts that are free of cosmetic defects. 5-3. Polypropylene Consumer and Injection Molding Containers, Crates, Garden Furniture, Housewares, Luggage, TSL, TWIM lyondellbasell. Weld lines create visible marks, but this type of injection molding defect can also reduce a part’s strength and durability. Plastic injection molding has long been an affordable and efficient process for producing custom prototypes and end-use production parts. 4. Knit Line occurs where different flow fronts of material meet while flowing through the mold. A weld or meld line is a weakness or visible. Weld lines often leave witness marks in the moulding surface. land and using maximum vent depths to get them as close to self-cleaning as possible. This will help the mold designer to determine the allowable gate and knit line locations. Using three test materials, polystyrene (PS), polycarbonate (PC) and polyoxymethylene (POM), the relationship between a design and a processing parameter. It is one of the most common blemishes for manufactured products. As the melted plastic fills the mold, there are locations where the molten plastic flow stream separates and then comes back together. A knit line is the spot where two flows meet. Injection molding is a popular manufacturing process used to fabricate parts in large volumes. Additional venting along the parting line perimeter will improve overall venting significantly. It emerges and becomes visible when the flow fronts cannot mold or knit during the molding process. Knit lines are formed in injection molding when two flow fronts meet in the middle of a part (a line where two sides of the. Disadvantage: May rust if improperly stored. Injection moulding (U. Insert injection molding is a process that requires an insert — typically metal — to be pre-placed in the tool for injected plastic to flow around. These lines usually occur around holes or obstructions and cause locally weak areas in the molded part. Knit lines appear to be a faint line or a crack in the finished part after it comes out of the injection mold. Strength at the knit line can be as little as 20% of the. Parts as thin as 0. Reduce the temperature of the mold and plastic being injected. 3 To get the most out of your Xometry Injection Molding experience, we offer the following part Design Guide with. Knit lines don’t always compromise the structural integrity of plastic parts. Raising the mold temperature will keep the material molten longer, resulting in stronger weld lines and even elimination of weld lines. (1. A weld line refers to a line, notch or color change that is created on the molded part caused by the convergence of two separate flows of molten plastic. Flashing can be a common defect in injection moulding and can affect the appearance and functionality of the finished product. Meld and knit lines are actually both different types of weld lines. Injection molding is the process of injecting liquid thermoplastic into a mold. 040-in. Contact Us. We then. Weld lines are a common imperfection to be found in most plastic injected molded parts. Our plastic injection molding glossary provides key terms. and to identify potential knit lines. 060 and 0. This occurs wherever there is a hole, notch, or any other feature on a part which divides the flow of plastic into 2 separate “flow fronts. A weld line refers to a line, notch or color change that is created on the molded part caused by the convergence of two separate flows of molten plastic. The most common and one of the most challenging injection molding defects are weld and knit lines. Notched weld lines then remain near the cavity walls. New blog post is up! What Are Knit Lines in Injection Molding, and How Do You Prevent Them? #injectionmolding #moldsmart #howto #rjg…Injection moulding is a well established mass production tool for polymeric products of all shapes and sizes which is now drawing the attention of companies and researchers who seek to utilise this high throughput fabrication technique to produce devices with nanoscale dimensions []. 0 and Table 1). Parting lines lie along the edge of the molded part, between the core and the cavity. As the polymer resin is injected into a mold, it flows through all parts of the mold. In a plastic injection-molded component, a knit line occurs when 2 different plastic flows emerge in a mold. Left: L-shaped perform. 4. Why. com support@makenica. In fact, strength at the knit line can be as little as 20 percent of the nominal strength of the part. Mold venting is critical to the quality and consistency of the finished part. The plastic in the ‘flow front’ cannot pass through the core pin, so it flows around the core pin splitting into 2 distinct flow fronts. Our Injection Molding Capabilities • Horizontal Injection Molding up to 3300 TONS • Structural Foam Molding + Structural Web • 1oz to 600oz part capacity. Depending on the material you use, the knit lines could be invisible or obvious—work with an injection molding company to figure out how to reduce the mold lines on your product. ) are easy to produce. Using restrictors helps push visible knit lines into less conspicuous areas. But add 30% glass and weld-line strength retention drops to only 34% as high as the compound with no weld line. 0 mm) is crucial to ensuring that parts cool evenly. Knit lines, also known as weld lines, are fine lines that resemble hairline fractures or cracks. There are times when porous materials like Porcerax are used in problem or backfill areas. Weld / Knit Lines; Assumptions. Injection molding is the predominant manufacturing process used for producing transparent polymer products. The Goldilocks principle applied to wall thickness. The weld-lines are undesirable from both aesthetic and functional points of view and their effect is different for varied materials, process conditions, loadings, forms. Compression molding produces solid parts that are free of flow and knit lines. Three terms that often get mixed up are weld, meld, and knit lines. Use a thread with a pitch greater than 0. Plastic injection molding is the industry’s most common way to manufacture parts. From the start of your project, you can count on The Toolroom to exceed your expectations for all of your plastic injection molding needs. As. They are formed when two or more flow frontINJECTION MOLDING GUIDE V2. Swirling can increase depending on the material you use, and the texture or polish of injection molding tools. 08 KICKOFF PRODUCTION. Whenever possible, vents should be located in the movable half of the mold wherever a gas void or knit line is seen on a part. After the solidification of molten plastic, the finished part is ejected out. Gating. In an injection mold, the plastic fluid flows and spreads out in many directions as it comes out of the gate. Injection molding is the most cost-competitive technology for manufacturing high volumes of identical plastic parts. M. This line does not normally impact the overall shape or dimensions of the item. 203 in. 5. 0 to 3. Injection moulding (U. ” What else can you do about weld lines—besides redesigning the mold or gate locations or adjust the flow pattern during fill with sequential valve gating? I recently saw a report on this issue from Moldex3D, the maker of molding simulation software. Increase injection speed.